In an effort to enhance security, recent network systems employ a plurality of communication and authentication methods. An external device connected to a personal computer (hereinafter abbreviated as “computer”) via a network has predetermined supported methods from among the plurality of communication methods and authentication methods. Accordingly, the computer must select and set a combination of communication and authentication methods supported by the external device from the plurality of communication and authentication methods.
An image-forming device disclosed in United States Patent Publication No. 2003/0226039 (corresponding to Japanese Patent Application Publication No. 2004-54893) selects one method from a plurality of authentication methods in order from highest security and attempts to connect to an external device using the selected authentication method. If the external device does not support the selected authentication method, the image-forming device temporarily disconnects from the external device, selects the next authentication method in order of highest security, and reconnects to the external device. The image-forming device continues to select authentication methods in this order from highest security to lowest until an authentication method supported by the external device is selected.